1. Field of the Invention
This invention relates to apparatus for applying pressure-sensitive adhesive labels and is particularly directed to such apparatus wherein pressure sensitive labels are peeled from a web of release paper or other backing material and are thereafter applied to products of their containers in a conveyor line.
2. Brief Description of the Prior Art
Conventional label applicators for applying pressure-sensitive (PS) labels to articles generally draw a web of release paper or other release coated material over a knife-edge peeler, so that the labels are separated from the web. The separated labels can then be applied to the goods moving past.
The labels may be applied directly to the articles, but it is often preferable to use a label applicator head which can hold each separated label, for instance through the use of suction and from which the label is applied to a particular product when the latter moves to a predetermined position relative to the head.
Heretofore, labeling machines have been proposed incorporating a label applicator head having a vacuum housing with a grid formed of an open network of support members at one side thereof to receive the separated labels, a blower or suction pump to create a partial vacuum to hold the separated label against the open grid, and a compressed-air jet system to provide blasts of compressed air through air hoses with open ends disposed over the position of the label, so that the label is propelled away from the grid and against a product to be labelled.
Unfortunately, such machines have been constructed so that the vacuum housing has exhibited a number of deficiencies. For example, in several types of housings the labels were not positively and firmly held against the open grid during the appropriate portion of the machine cycle. In addition,the housing often was connected with a machinery cabinet enclosing the moving drive train for the machine, and slitting dust was drawn from the web through the applicator head and into the machinery cabinet. This slitting dust can lead to wear of the drive mechanism, and can cause misoperation of electrical and electronic control circuits for the labeling machine.
Further, in the conventional labeling machines, if compressed air is used to propel the label against an article, hoses are connected directly between the support members forming the open grid, and the distance which a label can be accurately and effectively propelled thereby is limited because of aerodynamic disruptions associated with the exit of the compressed air from the hoses.
Also, in the conventional labeling machines, access to the inside of the vacuum housing has been limited, thereby making it somewhat difficult for an operator to adjust the positions at the grid that the compressed air hoses are situated and to conform them with the particular shape of the labels being used.
It is convenient to supply the PS labels on a roll of release backing paper disposed on a reel or bobbin, and to mount the roll on a supply hub of the labeling machine. However, in order to retain the roll on the hub, a set-screw-type locking ring has been used. This type of locking ring requires special tools and makes if difficult for an operator to remove one roll of labels and install another.
Still further, it has been difficult to provide a labeling machine with accurate timing means to synchronize the feeding of the labels and the application of the labels onto the articles, while affording flexibility in the speed at which the product line can be run.